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Date May 2014 Marks available 2 Reference code 14M.3.HL.TZ1.26
Level Higher level Paper Paper 3 Time zone Time zone 1
Command term Outline and State Question number 26 Adapted from N/A

Question

This question is about the standard model.

The Feynman diagrams show two electroweak interactions between electrons. The particle represented by the wavy line is a photon.

State

(i) the name of the exchange particle represented by the dotted line.
(ii) one difference between the two exchange particles.

[2]
a.

Outline how the observation of the interaction represented by the diagram with the dotted line provides evidence for the standard model.

[2]
b.

Markscheme

(i) Z (boson) / Z0 / boson;

(ii) Z is massive/has mass;

a.

neutral current interaction (mentioned);
which is only observed with a weak/electroweak (interaction);
as predicted by the standard model;

b.

Examiners report

This was generally well answered by well prepared candidates. Many identified the Z boson in (a)(i).

a.

In (b), incorrect answers were rare. Candidates with sound knowledge answered well and others did not answer at all.

b.

Syllabus sections

Core » Topic 7: Atomic, nuclear and particle physics » 7.3 – The structure of matter
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